Device for processing differently shaped workpieces

ABSTRACT

A device is provided for the automatic processing of differently shaped workpieces having a controlled tool-changing capability which permits a quick change of the set of tools in the device. This enables optimum adjustment of the tools to be made economically outside the production line. It also enables several different moveable and interchangeable tool frames to be located and moved on a lower frame into a variety of configurations. One tool frame is used at a time and when it is required to switch, several simple steps enable one tool frame to be moved to one side of the lower frame and a second tool frame to be moved into the operating position.

BACKGROUND AND DISCUSSION OF THE INVENTION

The present invention relates to a device for the automatic processingof differently shaped workpieces which has a controlled tool-changingcapability. The tool changing device of the present invention isparticularly useful for the spot-welding of parts or workpieces.

Previous tool-changing devices typically consist of a frame havingseveral different tools which are brought into use alternativelyaccordingly to the operational steps in an existing program orprocessing routine. Several of these devices can be arranged andinterconnected by intermediate conveyors one after the other whichtransport the parts to be processed to the devices, thereby forming aproduction line.

An object of the present invention is to develop an improved processingand tool-changing device which provides for a quick change of thecomplete set of tools in the device as well as in the workpiecereceiving fixture. The present invention, provides a device having animproved adaptability to accommodate different workpieces and wherein aquick tool change and an optimum adjustment of the tools outside theproduction line can be made in an economical manner, even underoperating conditions.

Preferably, the tool-changing device comprises a lower frame and aplurality of tool frames which are of identical construction and areplaced onto the lower frame. Fortunately many identical parts can beused in the tool-changing device of the present invention even though itis capable of accommodating workpieces of very different shapes.Alternately, the tool frames can be displaced on the lower frame along alongitudinal guide into a central working position. In this centralworking position, the workpieces are fed to the tool frame and areprocessed by the variety of tools arranged in the tool frame. If thereis a workpiece of a different shape or if a workpiece of the same typeis to be processed in another manner, the current tool frame is moved toone side and a different tool frame which is now required is displacedfrom the other side into the central working position. By this design,it is possible, in the case of workpieces of considerably differentshapes or requiring varying processing operations, to change the toolsvery quickly. Moreover, if a plurality of these devices are arranged oneafter the other in a production line or even if devices of this type areused at various locations or by various manufacturers, the same lowerframes and the same tool frames can always be used with the result thatthe manufacturing costs are considerably reduced.

Preferably, the individual tool frames are equipped only with differenttools enabling one to adjust the tools externally thereby reducing theadjustment time needed during production. Positioning new tools orarranging them in conjunction with a new part no longer needs to be donein the production line Also, the tool frames can be easily exchanged bymeans of a crane or a fork lift truck, since, in contrast to previoustool changing devices, the frame and the tools are completely separate.

The present invention is especially useful in spot-welding operationsusing electrode holders or production sequences with lowcounterpressure. Pinning is appropriate when working with largepressures. Although the present invention, in principle, can be used forparts of the most varied orders of magnitude, it is especially useful inthe case of medium-sized parts.

In contrast to the present tool-changing devices which are designed as aunit, and in particular such devices used for welding, the lower frame,the tool frames and the conveying mechanism of the present invention canbe reused and are fully reutilized. For example, after an initialproduction run, it is possible for tool frames having the tools fixedtherein to be removed and used later for a production run for spareparts without any modification.

The tool frames in the present invention are moved into the workingposition over the central section of the lower frame by a displacingunit. A variety of devices known to one skilled in the art can be used.For example, a pneumatic device which has a rodless cylinder thatenables strokes of over 2 meters can be used advantageously as thedisplacing unit. Another feature of the present invention is that thetool frames can be centered in position above the central section of thelower frame (i.e. the working position) by a centering unit and thenfastened by means of a clamping unit.

The tool frames themselves comprise a base plate and a head plate whichare connected to one another by a plurality of columns. The tools arefastened to either the head plate, the columns, or both. In order topermit the easy installation and removal of the tools and to combine aplurality of devices one after the other in a production line, it ispreferable if the workpieces can be passed through the device from oneside. The free accessibility thereby created not only enables improvedinsertion and removal of the workpieces, but also facilitatesmaintenance work, such as the replacement of electrode caps in a devicehaving welding tools.

Provided in the base plate of the tool frame is a recess into which thebottom plate of a workpiece holder is inserted. In the area of thisbottom plate, a lifter is arranged in the central section of the lowerframe. A table closing off the lifter at the top can be connected to thebottom plate of the workpiece holder by a second centering and clampingdevice. By the two centering and clamping devices, one for securing thetool frame to the lower frame and the other for securing the workpieceholder to the lifter, an arrangement is created which permits precisionwork to be performed on the workpiece.

The table connected to the bottom plate of the workpiece holder can bemoved by a controlled drive (e.g. a three-phase flat-geared motor) froma lower insertion position into an upper processing position enablingthe tools to act on the workpiece. The workpiece holder can be lifted inthe reverse direction to such an extent that when the centering devicesand clamping devices are released, it is possible to displace the toolframes on the longitudinal guide to beyond the table.

The tool frames in the present invention can have a variety ofarrangements. The first arrangement consists of only one tool framemounted over the central section of the lower frame. With thisarrangement, there is no direct means of changing the tool frame,however, the advantage of this device is that it can be used inconjunction with other similar single tool frame devices by linkingseveral of them together. The result is the same as if a device having asimple changing means for the tool frames is used. The secondarrangement utilizes a lower frame having a central section, a left handsection and a right hand section which are arranged next to one anotherin a row and provided thereon are two tool frames for alternating use.When not in use, the tool frames are stored in the left and right handsections. The third arrangement consists of a central section, two lefthand sections and two right hand sections. This arrangement permits thealternative use of three tool frames.

This third arrangement is particularly advantageous since it enables thealternate use of the three tool frames. In this arrangement, the lowerframe and the displacing unit are extended beyond the left hand sectionand the right hand section of the two-tool frame arrangement for formingthe additional locating surfaces for the third tool frame. Preferably,the individual sections are arranged in a U-shape rather than a straightline which makes it more convenient to alternately use the three toolframes. It is of course also possible, by enlarging the lower frame, toincrease the number of tool frames which can be alternatively used,however, this does not necessarily create any advantages which could notalso be gained by interlinking a plurality of these devices one afterthe other with a conveying means between them.

In all these arrangements, the same tool frames can be used andexchanged one for the other. In addition, the central section having thelifter can be used in any of these arrangements. Similarly, the outersections in the second and third arrangements conveniently are madeusing identical elements which are joined by a suitable connectingmeans.

Each tool frame can be provided with a separate conveying means by whichthe workpiece can be automatically picked up, inserted into theworkpiece holder and moved out of the device after processing iscomplete. In a further development of this feature, each tool frame canhave a separate drive for each conveying means arranged thereon. Theconveying means enables a workpiece to be picked up, inserted into theworkpiece holder, and once processing is complete, moved out of thedevice. Many different types of conveying means can be used as oneskilled in the art would know.

Fully automatic conveying is also possible in the present invention ifthe conveying means of the tool frame receives the workpiece from oneconveyor and after the processing is finished places it onto anotherconveyor. When a plurality of devices according to the present inventionare coupled, it is also possible for the preceding conveyer to depositthe workpiece on a lifter between the two devices in such a way that theconveyor of the following tool frame can pick it up. An intermediateconveyor having a lifter (for example, a translational rocking arm) maybe necessary with lower frames having the U-shaped configuration.

The power supply and the means for controlling the tools in the toolframes of the present invention can be effected by lines or cablespreferably from one or more locations above the tool frames.Cable-trailing devices can also be used to enable the tool frames to bemoved. Thus, contact reels and complicated transmission devices can beavoided. Moreover, when the cables are secured on each tool frame insuch a way as to be easily releasable (for example, by connectors orquick-acting couplings), the tool frames can be dismantled very quicklyand cost-effectively. Further work for replacing a tool frame is notreally necessary.

Preferably, the tool frames of the present invention are easilydisplaceable with the help of a support means such as spring-mountedball castors located on the lower frame. With this arrangement, thesprings are designed in such a way that they apply, as a whole, a largerupward force than the force due to the weight of the tool frame.Consequently, when the tool frame is being clamped down, it is onlynecessary for the clamping device to overcome the difference betweenboth forces. This difference in force can be accurately established bythe selection of the springs so that only small forces are required forthe clamping itself.

The tool-changing operation of the present invention using an automaticcontrol will now be described. Starting with a device having a lowerframe comprising a central section, a left hand section and a right handsection, the tool frames each occupying an outer position on the lefthand and right hand sections, the displacing unit is first moved towardthe selected tool frame. Once the end position is reached, pinning takesplace, i.e. a positive connection is made between the tool frame and thedriver of the displacing unit. Once pinning is effected, the displacingunit pulls or pushes the tool frame over the central section of thelower frame. Next, the centering units move out of the lower frame andthen the clamping units which pull the tool frame against the centralsection of the lower frame.

Once the tool frame is fixed on the central section of the lower frame,the workpiece holder arranged on the tool frame is centered with thelifter located in the lower frame. For this purpose, the table of thelifter is provided with a corresponding centering device which interactswith the bottom plate of the workpiece holder. Following the centeringoperation, both parts are fastened by means of a separate clampingdevice.

The operation of mounting the workpiece and the subsequent processingcan now begin. During this procedure, the part or workpiece to beprocessed is placed in front of the working station into the conveyorlocated in the tool frame and moved by the conveyor into the workpieceholder which is in the receiving position. The workpiece holder is thenraised by the lifter to take the part to be processed out of theconveyor and move it up into the processing position. While the part isbeing processed, the conveyor can return so that, once processing iscomplete and the workpiece holder has been lowered, it can move theprocessed part out of the tool frame and also introduce a new part intothe tool frame.

If the tool frame is to be changed for carrying out another processingphase or for processing a workpiece of a different configuration, thisis done by releasing the clamping device, the centering devices of thelifter and the lower frame, by the displacing unit moving the tool framewhich is no longer required to the side and then moving the new toolframe onto the central section of the lower frame. It is more convenientif the displacing unit has to perform only rectilinear movements. Aplurality of displacing units, (air cylinders for example), are neededfor movement in more than one direction such as in the case of the lowerframe with sections arranged in a U-shape.

Other details, objects and advantages of the present invention willbecome more readily apparent from the following description of apresently preferred embodiment thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, a preferred embodiment of the invention isillustrated, by way of example only, wherein:

FIG. 1 shows a front view of a device for the automatic processing ofdifferently shape workpieces;

FIG. 2 shows a plan view of the device shown in FIG. 1; and,

FIG. 3 shows a side view of the device shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A device for the automatic processing of differently shaped workpiecespreferably consists of a frame 5 having a central section 7, a left handsection and a right hand section 11. Tool frames 13 and 15 are placedonto the lower frame 5. In their dimensions and connections, both toolframes 13 and 15 are of identical construction. They preferably consistof a base place 17, a head place 19 and also perpendicular columns 21connecting the base plate 17 and the head plate 19. A variety of tools23 for processing a workpiece are fastened to the head plates 19. In thepresent device, which is designed for spot-welding, the tools 23 canalso be fastened to the columns 21. These are mainly electrode holders.

On their underside, the base plates 17 of the tool frames 13 and 15 areprovided with spring-mounted ball castors 25 whose springs are designedin such a way that they apply, as a whole, a larger upward force thanthe force due to the weight of the complete tool frame so that the toolframe can be easily moved and clamped down with little force. Here, aforce which corresponds to the difference between the spring force andthe force due to the weight is sufficient to clamp down the tool frame.

As shown in FIG. 2, a rectangular recess 27 is provided in the centerarea of the base plate 17 of the tool frame 15, shown in greater detailin this figure. The bottom plate 29 of a workpiece holder 31 is mountedin this recess 27 in a floating manner on disk-spring stacks inconjunction with coarse-centering devices.

In the area beneath the workpiece holder 31, the central section 7 ofthe lower frame 5 is equipped with a lifter 33. The lifter 33 is closedoff at the top by a table 35.

Referring to FIG. 2, the lower frame 5 is of a U-shaped construction andincludes a total of five locations at which tool frames can be mounted,thus enabling three tool frames to be moved in such a way that each toolframe can alternatively be brought into use over the central section 7of the lower frame 5. In the drawing, the tool frames 13 and 36 are onlyindicated, whereas the tool frame 15 is reproduced in detail withouthead plate 19 and tools 23.

To enable the tool frames to be moved in a desired manner over thecentral section 7, a total of four displacing units 37, 39, 41 and 42are provided. These displacing units are characterized by a rodlesscylinder having a pneumatic actuation, permitting larger strokes (over 2m) to be achieved without problem. Each displacing unit has a driver 43to engage allocated bores in the base plate 17 of the tool frames. Forthis purpose, each driver 43 consists of two pneumatic cylinders 49, adriving plate 51 and connecting pins 53. To move the tool frames, thedriver 43 is first moved toward the tool frame up to its bores 45 and47, respectively. The connecting pins 53 are then extended, insertedinto the bores 45 and 57, respectively, and moved into the desiredposition by the displacing unit, whose main component is a pneumaticallyacting rodless cylinder.

If this position is not the central section 7, in which the processingis carried out, but another section of the lower frame 5, the tool frameis secured in this position by means of two pinning units 55 each. Thepinning units comprise hydraulic cylinders 57 and centering points 59,the points interacting with bores 61 in the base plates of the toolframes. If tool frame 15 is located above the central section 7 of thelower frame 5, the tool frames are accurately secured in their workingposition by centering units. The tool frames are additionally clampeddown in the working position by means of four hydraulically drivenswivelling clamping cylinders 63. Only a small force is necessary toclamp down the tool frames mounted on spring-mounted ball castors, sothat swivelling clamping cylinders 63 of relatively small dimensions canbe used.

If the tool frame 15 is centered and firmly connected to the lowerframe, the bottom plate 29 of the tool holder 31 mounted in the recess27 of the base plate 17 is connected in a similar manner to the table 35of the lifter 33. Here, too, centering devices 65 are provided which,with their tips, engage bores 67 in the bottom plate 29. A centralclamping device 69, likewise formed by a swivelling clamping cylinder,is provided to clamp the bottom plate 29 down onto the table 35.

The actual operation of the tool-changing device will now be described.First, the workpiece is inserted into the workpiece holder 31. This canbe done by a worker as shown in FIG. 3 or it can be performedautomatically by means of a suitable apparatus. The workpiece is thenmoved up into its processing position. The lifter 33 located in thecentral section 7 of the lower frame 5 is provided for this purpose. Thelifter 33, preferably, comprises an electric-motor drive in the form ofa three-phase flat-spur-gear motor and a crank. The lifting movement iscontrolled by means of a precision switching mechanism. Once theoperating height is reached, the tools 23 start the programmedprocessing of the workpiece. In the embodiment shown in the drawings,the tools 23 are mainly formed by electrode holders.

Once the processing of the workpiece has been carried out, the lifter 33lowers the table 35 and with it the workpiece holder 31. During thismovement, the processed part is deposited in the return conveyor device71 and is then conveyed out of the tool frame 15 where it is received byan intermediate conveyor which deposits the part onto the conveyingdevice of the next processing station. In the meantime, the workpieceholder 31 can receive another workpiece.

Just as each tool frame has a workpiece holder for accommodating acertain workpiece and its adapted tools, each workpiece frame is alsoequipped with separate conveying device 71. The drive of the conveyingdevice 71 preferably consists of a change-pole worm-gear motor 75,conveying members with roller blocks 77, and also cam strips 79 whichinteract with a camshaft gear 81 for controlling the conveying step.

If other processing operations are to be carried out on the sameworkpiece in the same device or if the processing of a workpiece of adifferent shape should be desired, the device of the present inventiondoes not need to be converted. To the contrary, another tool frame onlyneeds to be moved into the working position over the central section 7of the lower frame 5. For this purpose, it is first necessary for thetool frame 15 located in this position to be moved out, such as to theright in FIG. 2. Before this can be done, however, the clamping device69 must be released, the centering device 65 must be retracted such thatthe workpiece holder is free from lifter 33, the swivelling clampingcylinders 63 must be released and the pinning units 55 must be retractedsuch that base plate 17 of the tool frame 15 is free from the lowerframe 5. The connecting pins 53 of the driver 43 can now engage thebores 47 in the base plate 17 and the displacing unit 39 can move toolframe 15. Once the right hand position has been reached, tool frame 15is secured by the pinning units 55, which again engage the bores 61 ofthe base plate 17. With displacing unit 37, it is possible to move thetool frame 15 at right angles to the step just described and into awaiting position further away.

The displacing unit 42 now moves up to the tool frame 13, couples ontoit and pulls it into the processing position above the central section7. The centering and clamping operations described above are thencarried out in this position so that, subsequently, a new processingphase with changed tools can be carried out.

The tool frames can be easily moved by means of the displacing units 37,39, 41 and 42 on the lower frame 7 in such a way that one of the threetool frames can always be brought into the working position. It is alsopossible to remove the tool frames from the lower frame by lifting themoff using lugs 83. The tool frames can then be used in other similardevices either at the present site or at other sites. The tool framescan also be lifted off when the tools 23 have to be changed or replacedfor a new workpiece. Since the tool frames always contain all tools fora particular phase of processing and also the conveying device fortransporting the workpiece, it is now possible with the presentinvention, to carry out the positioning of tools for a new workpieceoutside the actual production line (i.e. the center section) so that theactual production sequence is not disturbed.

In order to permit an easy exchange of the tool frames, all lines forsupplying power and control signals to the device are preferably madevia plug connections (not shown) on the tool frames which areconstructed so as to be easily releasable. So that easy displacement ofthe tool frames on the lower frame is ensured without great expense, thepower and control lines are fed to the individual tool frames fromabove, preferably through cable-trailing means.

The actual control signals for the device has not been discussed indetail because they can easily be realized by one skilled in the artfrom the information provided herein. If a specific program isspecified, the device including the required changes of the tool framescan operate fully automatically. If used in combination with anoperator, it is possible for the operator to not only insert theworkpieces but also to give the commands for changing the tool frames.

While a presently preferred embodiment of practicing the invention hasbeen shown and described with particularity in .connection with theaccompanying drawings, the invention may otherwise be embodied withinthe scope of the following claims.

What is claimed is:
 1. A controlled tool-changing device for theautomatic processing of differently shaped workpieces, comprising:(a) alower frame comprising a central section, a left hand section and aright hand section, a longitudinal guide on an upper side of the lowerframe by means of which a plurality of tool frames can alternately bemoved by a plurality of displacing units from an outer position into aposition over the central section of the lower frame where it can befixed by a first centering unit and a first clamping unit; (b) each toolframe comprising a base plate having a recess into which a bottom plateof a workpiece holder is inserted, a head plate, a plurality of columnsconnecting the base plate to the head plate, and a plurality of toolsfastened therein; and (c) the central section of the lower framecomprising a lifter having a table located thereon such that (i) thetable is smaller in its dimensions than the recess in the base plate ofthe tool frame, (ii) when the tool frame is fixed above the centralsection the table can be connected to the bottom plate of the workpieceholder by a second centering unit and a second clamping unit, and (iii)the workpiece holder can be lifted such that it is possible to displacethe tool frame on the longitudinal guide to beyond the table; and (d) acontrolled drive for moving the table connected to the bottom plate ofthe workpiece holder from a lower insertion position into an upperprocessing position enabling the tools to act on the workpiece.
 2. Thedevice according to claim 1, wherein the plurality of tool framescomprise three tool frames such that for the alternate use thereof, thelower frame and the displacing units are extended beyond the left handsection and the right hand section to form additional surfaces forsupporting a tool frame.
 3. The device according to claim 2, wherein thesections of the lower frame form a U-shaped arrangement.
 4. The deviceaccording to any one of claims 1 to 3, wherein each tool frame isprovided with a conveying device for automatically picking up theworkpiece, inserting it into the workpiece holder, and after processingis complete, moving it out of the device.
 5. The device according toclaim 4, wherein each conveying device has a separate drive unit.
 6. Thedevice according to any one of claims 1 to 3, wherein power and controlsignals for the tools in each tool frame are supplied by cables from oneor more locations above the tool frame and wherein cable-trailingdevices are used to enable the tool frames to be moved.
 7. The deviceaccording to claim 4, wherein power and control signals for the tools ineach tool frame are supplied by cables from one or more locations abovethe tool frame and wherein cable-trailing devices are used to enable thetool frames to be moved.
 8. The device according to claim 6, wherein thecables are secured on each tool frame in such a way as to be easilyreleasable.
 9. The device according to claim 7 wherein the cables aresecured on each tool frame in such a way as to be easily releasable. 10.The device according to any one of claims 1 to 3, further comprisingspring-mounted ball castors located on the lower frame for assistingdisplacement of the tool frames, the springs being designed in such away that they apply, as a whole, a larger upward force than the weightof the tool frame.